BOAS spring clip

ABSTRACT

A clip for an air seal assembly, comprising a clip base having a control ring interface; a biasing element coupled to the clip base opposite the control ring interface; wherein the clip is insertable into a clip receiver and configured to engage a notch of a blade outer air seal and configured to detachably couple with a clip mounting flange.

BACKGROUND

The disclosure relates to a spring clip for a ceramic matrix composite(CMC) laminated blade outer air seal (BOAS) with an axially facing coremandrel.

An axial flow, gas turbine engine has a compression section, acombustion section and a turbine section. An annular flow path for theworking fluid extends axially through the sections. A stator assemblyextends about the annular flow path for confining the working fluid tothe flow path and for directing the fluid along the flow path.

As the working fluid flows along the flow path, the working fluid ispressurized in the compression section and burned with fuel in thecombustion section to add energy to the working fluid. The hot,pressurized working fluid is expanded through the turbine section toproduce work. A major portion of this work is used for driving a freeturbine or developing thrust for an aircraft.

A remaining portion of the work generated by the turbine section is notused for these purposes, Instead it is used to compress the workingfluid itself. A rotor assembly extends between the turbine section andthe compression section to transfer this work from the turbine sectionto the compression section. The rotor assembly in the turbine sectionhas rotor blades which extend outwardly across the working medium flowpath. The rotor blades have airfoils, which are angled with respect tothe approaching flow to receive work from the working fluid and to drivethe rotor assembly about the axis of rotation.

An outer air seal circumscribes the rotor blades to confine the workingfluid to the flow path. The outer air seal is part of the statorstructure and is formed of a plurality of arcuate segments. The statorassembly further includes an outer case and a structure for supportingthe segments of the outer air seal from the outer case. The outer caseand the support structure position the seal segments in close proximityto the blades to block the leakage of the working fluid past the tips ofthe blades. As a result, the segments are in intimate contact with thehot working fluid, that receives heat from the working fluid and arecooled to keep the temperature of the segments within acceptable limits.

The use of ceramic matrix composite blade outer air seals require largecontact areas to reduce delamination risk and reduce bearing loads. Aceramic matrix composite blade outer air seal that includes many radialfeatures inherently creates high thermal gradients. Axially installedBOAS require an attachment feature to keep them connected to the controlring. These parts can be complicated to manufacture as well as install.BOAS also need to be preloaded for low speed operations.

Accordingly, it is desirable to provide a spring clip that enables analternative efficient system and method to assure a proper outer airseal to blade tip interface that can be individually installed orremoved, while reducing the stresses from thermal gradients.

SUMMARY

In accordance with the present disclosure, there is provided a clip foran air seal assembly, comprising a clip base having a control ringinterface; a biasing element coupled to the clip base opposite thecontrol ring interface; wherein the clip is insertable into a clipreceiver and configured to engage a notch of a blade outer air seal andconfigured to detachably couple with a clip mounting flange.

In another and alternative embodiment the blade outer air seal comprisesa blade outer air seal control ring comprising: a leading edge side anda trailing edge side opposite the leading edge side, a hook protrudingaxially from the trailing edge side, the clip receiver communicatingthrough the blade outer air seal control ring from the leading edge sideto the trailing edge side, the clip mounting flange extending from thetrailing edge side proximate the receiver; a blade outer air sealcoupled to the blade outer air seal control ring, the blade outer airseal comprising: a body having a leading edge and a trailing edgeopposite thereof, a pocket formed into the body having an upper regionand a lower region, the pocket configured to receive and engage with thehook; the notch being formed into the upper region, a shelf formed fromthe lower region extending axially outward from the pocket on thetrailing edge side of the body; and the clip insertable into the clipreceiver and configured to engage the notch of the blade outer air sealand configured to detachably couple with the clip mounting flange.

In another and alternative embodiment the blade outer air seal comprisesa ceramic matrix composite material.

In another and alternative embodiment the clip is configured to bebiased to retain the blade outer air seal engaged with the control ring.

In another and alternative embodiment the biasing element is configuredto detachably engage the clip mounting flange and the upper region ofthe blade outer air seal.

In another and alternative embodiment the clip is configured to preventaxial rotation of the blade outer air seal.

In another and alternative embodiment each of the plurality of bladeouter air seals are configured to be individually installed and removedfrom the blade outer air seal control ring.

In another and alternative embodiment the clip with the notch and thehook are configured as an anti-rotation feature to inhibit rotation ofthe blade outer air seal.

In another and alternative embodiment the clip base is formed to fitwithin the clip receiver.

In another and alternative embodiment the biasing element is configuredas a curved sheet with at least one of a U bend, S bend, and hook shapedprofile.

In another and alternative embodiment the biasing element is welded ontothe clip base opposite the control ring interface.

In another and alternative embodiment the clip is configured to employ aradial preloading force to trap the blade outer air seal in a mountedposition.

In another and alternative embodiment the clip base comprises a T crosssection configured to secure the clip in the clip receiver.

In an exemplary embodiment, the disclosure relates to a spring clip fora CMC laminated BOAS with an axially facing core. Two radial wallsextend axially from leading to trailing edges along the mating faces toallow intersegment feather seals and promote constant wall thickness.Centered on the outside diameter is a rectangular anti-rotation notch,which also receives a spring clip. The BOAS includes a constant wallthickness along the span of the BOAS. The constant wall thicknessreduces stresses from thermal gradients. The BOAS can be ship lapped aspart of the laminate preform to promote sealing and to trap featherseals. The axial cavity of the BOAS allows individual BOAS installationor removal and also promotes a large contact surface. The assemblyincludes a cobalt alloy spring clip that is axially assembled into afull hoop carrier ring to both anti-rotate the BOAS as well as provideradial preloading to trap the BOAS in the assembly.

In an exemplary embodiment, an axially installed spring clip isdisclosed. A wide control ring interface feature is located at thefront, followed by an anti-rotation feature and sheet metal spring/clip.The sheet metal region could be welded to the machined anti-rotationfeature. Four faces of the clip mate with a countersunk feature in thecontrol ring and the spring holds the BOAS in place, while providing apreloading force.

Other details of the clip for the ceramic matrix composite blade outerair seals are set forth in the following detailed description and theaccompanying drawings wherein like reference numerals depict likeelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an exemplary gas turbine engine;

FIG. 2 is a schematic representation of a blade and outer air sealportion of the exemplary gas turbine engine;

FIG. 3 is a cross section of an exemplary CMC pocket BOAS inserted intoa BOAS control ring with spring clip according to the disclosure;

FIG. 4 is a perspective view of the exemplary CMC Pocket BOAS of FIG. 3;

FIG. 5 is a perspective view of the trailing edge of the BOAS controlring with CMC pocket BOAS and spring clip of the configuration of FIG.3;

FIG. 6 is a perspective view of an assembly of multiple exemplary CMCPocket BOAS with a ship lap side to side alignment;

FIG. 7 is an enlarged view of ship lap side to side exemplary CMC PocketBOAS;

FIG. 8 is a perspective view of the BOAS control ring;

FIG. 9 is a perspective view of an exemplary spring clip;

FIG. 10 is a schematic cross sectional ply pattern of the core of anexemplary CMC pocket BOAS.

DETAILED DESCRIPTION

FIG. 1 shows a general partial fragmentary view of a gas turbine engine10 suspended from an engine pylon 12. The engine 10 typically includesin serial flow communication with a low pressure compressor driven fanassembly 14, a high pressure compressor 16, an annular combustor 18,high pressure turbine 20, and low pressure turbine 22. During operation,air is pressurized in the compressor and mixed with fuel in thecombustor for generating hot combustion gases which flow through thehigh and low pressure turbines that extract energy therefrom. The highpressure turbine 20 powers the high pressure compressor through a highpressure turbine/high pressure compressor shaft assembly 24 and the lowpressure turbine 22 powers the low pressure compressor fan assembly 14through a low pressure turbine/fan rotor shaft assembly 26. It should beunderstood that the shaft assembly 24, 26 may include various shaftswhich coaxially rotate in a common or counter rotation arrangement.

The exemplary engine 10 is in the form of a high bypass ratio enginemounted within a nacelle assembly 28 in which most of the airpressurized by the fan assembly 14 bypasses the core engine itself forgenerating propulsion thrust. The fan air F is discharged from theengine 10 through a fan nozzle section 30 defined radially between acore nacelle 32 and a fan nacelle 34. The core exhaust gases C aredischarged from the core engine through a core exhaust nozzle 36 definedbetween the core nacelle 32 and a center plug 38 disposed coaxiallytherein around an engine longitudinal centerline axis A of the engine 10and nacelle.

FIG. 2 is a schematic representation of a blade and outer air sealportion of the exemplary gas turbine engine. A blade outer air sealcontrol ring, or simply control ring 34 is shown. The control ring 34supports each individual blade outer air seal 36. The blade 38 is shownproximate the blade outer air seal 36. The blade outer air seals 36 aremounted to the control ring 34 in an axial fashion, along the enginelongitudinal centerline axis A.

Referring also to FIGS. 3-10, the control ring 34 includes a leadingedge side 40 and a trailing edge side 42 that is axially opposite theleading edge side 40. The control ring 34 includes an exterior 44 and aninterior 46 radially opposite the exterior 44. A hook 48 protrudesaxially from the trailing edge side 42 proximate the interior 46. Thehook 48 is arranged to support each blade outer air seal 36, thusmultiple hooks 48 are configured along the interior side 46 of thecontrol ring 34 to support the array of blade outer air seals 36. Thehook 48 is a relatively large structure that distributes the stressesacross the contacting surfaces between the blade outer air seal 36 andthe control ring 34.

A clip receiver 50 is formed from in the control ring 34. The clipreceiver 50 is shown as a rectilinear through bore open from the leadingedge side 40 to the trailing edge side 42. The clip receiver 50 isconfigured to receive a clip 52. The clip receiver 50 can be formed in avariety of shapes to match the clip 52 design.

The clip 52 is configured to be biased to retain the blade outer airseal 36 engaged with the control ring 34 and prevent axial rotation ofthe blade outer air seal 36. The clip 52 includes a clip base 54 formedto fit within the clip receiver 50. The clip base 54 is formed with athickness that snugly interfaces within the clip receiver 50 andprevents rotation that acts as an anti-rotation feature for the bladeouter air seal 36. In an exemplary embodiment, the clip base 54 can beconfigured as a T cross section to secure the clip 52 in the clipreceiver 50. The clip base 54 can include a control ring interface 55that matches the clip receiver 50. A biasing element 56 extends from theclip base 54 opposite the control ring interface 55. The biasing element56 is formed to retain the blade outer air seal 36 and press against theblade outer air seal 36 and a corresponding clip mounting flange 58. Inan exemplary embodiment, the biasing element 56 can be configured as acurved sheet with a U bend or S bend, hook shaped profile. In anexemplary embodiment, the biasing element 56 can be welded onto the clipbase 54 opposite the control ring interface 55. In an exemplaryembodiment, the clip 52 can comprise a cobalt alloy material, or otheralloy or material that exhibits good wear properties with the materialsof the control ring 34 and blade outer air seal 36. The clip 52 canprovide radial preloading to trap the blade outer air seal 36 in amounted position. The clip 52 is formed with the two regions, the clipbase 54 and biasing element 56 for structural anti-rotation and flexibleretention. The clip 52 is configured to preload the blade outer air seal36 for low speed operation of the engine 10. The clip 52 also enablesthe individual installation and removal of the blade outer air seal 36.The simplicity of the clip 52 design allows for use in multiple bladeouter air seal 36 configurations.

The clip mounting flange 58 is formed in the control ring 34 and extendsfrom the trailing edge 42 proximate the clip receiver 50. In anexemplary embodiment, the clip mounting flange 58 extends axially fromthe trailing edge flush with the blade outer air seal 36 as shown inFIG. 3. A clip mounting flange 58 can be associated with each bladeouter air seal 36 and clip 52, as shown in FIG. 5.

The blade outer air seal 36 is formed as a ceramic matrix compositematerial. The ceramic composite material blade outer air seal 36 can beformed from continuous fiber construction. FIG. 10 shows an exemplaryembodiment with the blade outer air seal core 60 formed via an overwrapof braids of fibers without lap joints. In an exemplary embodiment, thecore 60 can be configured from a single cavity or from two cavities. TheCMC blade outer air seal 36 can be produced around a core mandrel (notshown) with overwrap braids to simplify construction.

The blade outer air seal 36 includes a body 62 that has a leading edge64 and a trailing edge 66 that is opposite the leading edge 64. The body62 is generally a rectilinear configuration with a first side 68 and asecond side 70 opposite the first side 68 in parallel relationship. Thefirst side 68 and second side 70 are configured to be oriented axiallyparallel to the axis A of the engine 10. The leading edge 64 andtrailing edge 66 are configured to be parallel and align parallel withthe leading edge side 40 and trailing edge side 42 of the control ring34. The body 62 is also configured with an arcuate shape to match thecurvature of the control ring 34. The body 62 can include a constantwall thickness along the span of the blade outer air seal 36. Theconstant wall thickness reduces stresses from thermal gradients.

An axial cavity or simply pocket 72 is formed in the body 62 between anupper region 74 and a lower region 76. The pocket 72 extends between thefirst end side 68 and the second end side 70. The pocket 72 isconfigured to receive the hook 48 and engage the hook 48 to secure theblade outer air seal 36 to the control ring 34. The trailing edge 66 ofthe blade outer air seal body 62 is configured to align with the clipmounting flange 58 on the trailing edge side 42 of the control ring 34,as shown in FIG. 3. The pocket 72 allows for minimal radial features inthe blade outer air seal 36, thus improving the thermal gradientcharacteristics.

A notch 78 is formed in the upper region 74 of the body 62. The notch 78is configured to receive the clip 52. The notch 78 is configured to bealigned with the clip receiver 50 when the blade outer air seal 36 iscoupled to the control ring 34. In an exemplary embodiment, the notch 78is shaped to match the clip base 54 and receive the clip base 54. Theclip 52 biasing element 56 is configured to detachably engage the clipmounting flange 58 and the upper region 74 of the blade outer air seal36. The clip 52 along with the notch 78 and the hook 48 are configuredas an anti-rotation feature 80 to inhibit rotation of the blade outerair seal 36 when mounted to the control ring 34.

A shelf 82 is formed in the body 62 extending from the lower region 76.The shelf 82 extends axially outward away from the pocket 72 on theleading edge 64 side of the body 62. The shelf 82 mates to the interiorside of the control ring 34. The shelf 82 provides a leading edgesealing land on the blade outer air seal that extends axially from thepocket 72.

The body 52 further includes a chamfer 84 formed at each of the firstend 68 and the second end 70 opposite thereof. The chamfer 84 isconfigured to facilitate a ship lap 86 engagement along each of thefirst end 68 and second end 70 from the leading edge 64 to the trailingedge 66. The chamfer 84 also allows for an intersegment feather seal 88to be utilized between the adjoining blade outer air seals 36. Theintersegment feather seal 88 can have an “L” shaped cross-sectionconfigured insertable in the gap of the ship lap joint 86.

The benefit of the above described arrangement is to allow forindividual installation and removal of each blade outer air seal 36 fromthe blade outer air seal control ring 34. The individual blade outer airseal 36 can be replaced without the need to disassemble the entire BOASassembly. The individual blade outer air seal 36 can be mounted to thecontrol ring 34 by installing the upper region 74 of the BOAS body 62such that, the hook 48 is inserted into the pocket 72. The trailing edge66 of the blade outer air seal 36 is aligned flush with an extremity 90of the clip mounting flange 58. The clip 52 is inserted into the controlring 34 from the leading edge side 40 into the clip receiver 50 andengaged with the clip mounting flange 58 of the control ring 34, as wellas, the notch 78, the biasing element 56 presses against the clipmounting flange 58 and the upper region 74 and trailing edge 66 of thebody 74. The pocket 72 and hook 4 engagement promote a large contactsurface 92 that distribute stresses to reduce delamination and reducebearing loads.

The clip 52 gives the advantage to provide a simple way to secure,anti-rotate, and preload axially mounted BOAS with one part.

Another advantage of the clip 52 is that it only has three features,simplifying the manufacturing process.

Another advantage of the clip 52 is that the anti-rotation feature ofthe clip fits into a notch on the BOAS and the spring end hook thatclips over the side of the BOAS, preventing movement.

Another advantage is that the clip 52 is easily installed through a sloton the front of a BOAS control ring by pushing it until it clips ontothe BOAS. Once installed, the spring pushes on the BOAS, providing theneeded preloading force.

There has been provided a clip for a ceramic matrix composite bladeouter air seal. While the ceramic matrix composite blade outer air sealhas been described in the context of specific embodiments thereof, otherunforeseen alternatives, modifications, and variations may becomeapparent to those skilled in the art having read the foregoingdescription. Accordingly, it is intended to embrace those alternatives,modifications, and variations, which fall within the broad scope of theappended claims.

What is claimed is:
 1. A clip for an air seal assembly, comprising: ablade outer air seal control ring comprising: a leading edge side and atrailing edge side opposite said leading edge side; a hook protrudingaxially from said leading edge side; a clip base having a control ringinterface; a blade outer air seal coupled to said blade outer air sealcontrol ring, said blade outer air seal comprising: a body having aleading edge and a trailing edge opposite thereof, a pocket formed intosaid body having an upper region and a lower region, said pocketconfigured to receive and engage with said hook; a notch being formedinto said upper region, a shelf formed from said lower region extendingaxially outward from said pocket on said leading edge side of said body;said clip base insertable into a clip receiver and configured to engagesaid notch of the blade outer air seal and configured to detachablycouple with a clip mounting flange; a biasing element coupled to saidclip base opposite said control ring interface; wherein said clip baseis insertable into the clip receiver configured as a through bore in theblade outer air seal control ring extending from the leading edge sideto the trailing edge side and configured to engage the notch of theblade outer air seal and configured to detachably couple with the clipmounting flange formed in the trailing edge of the blade outer air sealcontrol ring, the clip mounting flange extending from said trailing edgeside proximate said clip receiver.
 2. The clip of claim 1, wherein saidblade outer air seal comprises a ceramic matrix composite material. 3.The clip of claim 1, wherein said clip is configured to be biased toretain the blade outer air seal engaged with the blade outer air sealcontrol ring.
 4. The clip of claim 1, wherein said biasing element isconfigured to detachably engage said clip mounting flange and the upperregion of said blade outer air seal.
 5. The clip of claim 1, whereinsaid clip is configured to prevent axial rotation of the blade outer airseal.
 6. The clip of claim 1, wherein said blade outer air seal can beconfigured as a plurality of blade outer air seals, each of saidplurality of blade outer air seals are configured to be individuallyinstalled and removed from said blade outer air seal control ring. 7.The clip of claim 1, wherein said clip with said notch and said hook areconfigured as an anti-rotation feature to inhibit rotation of said bladeouter air seal.
 8. The clip of claim 1, wherein said clip base is formedto fit within the clip receiver.
 9. The clip of claim 1, wherein saidbiasing element is configured as a curved sheet with at least one of a Ubend, S bend, and hook shaped profile.
 10. The clip of claim 1, whereinthe biasing element is welded onto the clip base opposite the controlring interface.
 11. The clip of claim 1, wherein the clip is configuredto employ a radial preloading force to trap the blade outer air seal ina mounted position.
 12. The clip of claim 1, wherein the clip basecomprises a T cross section configured to secure the clip in the clipreceiver.
 13. A clip for a blade outer air seal assembly, comprising: ablade outer air seal control ring comprising: a leading edge side and atrailing edge side opposite said leading edge side; a hook protrudingaxially from said leading edge side; a clip base having a control ringinterface; a blade outer air seal coupled to said blade outer air sealcontrol ring, said blade outer air seal comprising: a body having aleading edge and a trailing edge opposite thereof, a pocket formed intosaid body having an upper region and a lower region, said pocketconfigured to receive and engage with said hook; a notch being formedinto said upper region, a shelf formed from said lower region extendingaxially outward from said pocket on said leading edge side of said body;said clip base insertable into a clip receiver and configured to engagesaid notch of the blade outer air seal and configured to detachablycouple with a clip mounting flange; a biasing element coupled to saidclip base opposite said control ring interface; wherein said clip baseis insertable into the clip receiver configured as a through bore in theblade outer air seal control ring extending from the leading edge sideto the trailing edge side and configured to engage the notch of theblade outer air seal and configured to detachably couple with the clipmounting flange formed in the trailing edge of the blade outer air sealcontrol ring, the clip mounting flange extending from said trailing edgeside proximate said clip receiver; wherein said blade outer air seal canbe configured as a plurality of blade outer air seals each of saidplurality of blade outer air seals are configured to be individuallyinstalled and removed from said blade outer air seal control ring.
 14. Aspring clip for a blade outer air seal assembly, comprising: a bladeouter air seal control ring comprising: a leading edge side and atrailing edge side opposite said leading edge side; a hook protrudingaxially from said leading edge side; a clip base having a control ringinterface; the blade outer air seal coupled to said blade outer air sealcontrol ring, said blade outer air seal comprising: a body having aleading edge and a trailing edge opposite thereof, a pocket formed intosaid body having an upper region and a lower region, said pocketconfigured to receive and engage with said hook; a notch being formedinto said upper region, a shelf formed from said lower region extendingaxially outward from said pocket on said leading edge side of said body;said clip base insertable into a clip receiver and configured to engagesaid notch of the blade outer air seal and configured to detachablycouple with a clip mounting flange; a biasing element coupled to saidclip base opposite said control ring interface; wherein said clip baseis insertable into the clip receiver configured as a through bore in theblade outer air seal control ring extending from the leading edge sideto the trailing edge side and configured to engage the notch of theblade outer air seal and configured to detachably couple with the clipmounting flange formed in the trailing edge of the blade outer air sealcontrol ring, the clip mounting flange extending from said trailing edgeside proximate said clip receiver, wherein the spring clip is configuredto employ a radial preloading force to trap the blade outer air seal ina mounted position.